In 2267, following the breakdown of peace talks between the Federation and the Klingon Empire, the Federation-Klingon War broke out. The neutral planet of Organia, a strategic position between the two powers, became a political hotspot between the Empire and the Federation.

Part of Kor's invasion force on Organia

On stardate 3102.7, Commander Kor led a battalion of five hundred Klingon soldiers in an invasion and occupation of Organia, where he briefly became their military governor. As governor, Kor ruthlessly maintained order on the planet, ruling with an iron fist by maintaining a stringent list of rules, any violation of which was punishable by death. Unknown to Kor at the time, Captain Kirk, posing as an Organian, and Lieutenant Commander Spock, posing as a dealer in kevas and trillium, were among the subjugated. The two Starfleet officers mounted vain guerrilla attacks against Kor and his army. Meanwhile, in orbit around Organia, the Klingon and Federation fleets faced each other in battle.

Captain Kor (2269)

Once the hostilities between the two began to reach its climax, all ships suddenly and mysteriously became paralyzed and all weapons became superheated and temporarily rendered useless. Unknown to both sides at the time, the Organians were in fact an advanced non-corporeal species, despite their primitive way of life. As quickly as it started, the Organians effectively ended the occupation, the war, and Kor's governorship. (TOS: "Errand of Mercy") The Organians continued to promote peace between the two powers by imposing the Organian Peace Treaty. (TOS: "The Trouble with Tribbles")

Within two years, Kor became the commanding officer of the IKS Klothos. In 2269, Kor again faced his enemy, Captain Kirk, in battle when the Klothos engaged the USS Enterprise in the Delta Triangle region. During the battle, the two ships became entangled in a "time trap," a phenomenon unique to that region, pulling the ships into an alternate universe known as Elysia.

Kor attempted to escape but the Klothos was unable to break free from the region, partly due to its unusual properties, including draining dilithium crystals of their energy. Through cooperation, the crews of the Enterprise and Klothos were able to formulate a strategy by combining their warp power in an effort to overcome both ships' individual power deficiencies.

IKS Klothos (2269)

Prior to their attempt, however, Kor had one of his officers, Kali, plant a bomb-like device in the computer room of the Enterprise, set to explode once the starship cleared the phenomenon and reached warp eight. Both ships were able to escape the region, and the destruction of the Enterprise was averted, moments before the ship reached warp eight. Nevertheless, Kor claimed responsibility for formulating their combined escape and returned to Klingon space, no worse for the wear. (TAS: "The Time Trap")

Kor's ship, the Klothos, was one of the first Klingon vessels equipped with a cloaking device. Kor is said to have spent three days in the engine room taking it apart and studying it before their first mission. This proved critical when he later commanded one of the two Klingon divisions aboard the Klothos, along with Kang, in an attack against the Federation outpost at Caleb IV. During the attack, Kor successfully tricked his opponent by launching first a small initial attack, and then striking with the bulk of his forces when the Federation began repair efforts. (DS9: "Once More Unto the Breach")

During the late 2280s, a band of depredators, led by the Albino, began raiding Klingon colonies. Three Klingon warships, led by Kor, Koloth and Kang, were sent out to stop him. Their mission was successful, as they captured most of the depredators. However, the Albino was able to escape. In the Albino's last message to the Klingons, he promised to take his revenge on the firstborn of each of the three captains. Within the space of a few years, he kept his word and managed to infect the warriors' three innocent children with a genetic virus that eventually killed them all. (DS9: "Blood Oath")

In 2290, Kor, Kang, Koloth and Curzon Dax pledged a blood oath to avenge the deaths of the Klingons' sons, the offense committed by the Albino. They nearly caught him at Galdonterre, but one of their subspace messages was intercepted and he, once again, was able to escape.

Dahar Master Kor on Secarus IV (2370)

After decades of searching, Kang learned of the whereabouts of the Albino, in 2370, on the planet Secarus IV. Kang traveled to Secarus IV and discovered his compound. The Albino knew immediately of his arrival and invited the trio to a "fair fight" and one last, glorious battle. Kang contacted both Kor and Koloth for a rendezvous on Deep Space 9, in preparation of their final attempt to complete their lifelong quest.

Three months later, Kor, Koloth, and Kang, with the aid of Jadzia Dax, prepared their attack on the Albino's compound, only to discover that it was a trap. Using the element of surprise, they bombarded the compound with tetryon particles, forcing the Albino and his sentries into face-to-face, hand-to-hand combat. Koloth was fatally wounded fighting the Albino's personal guard. Following a fierce duel, Kang was able to slay the Albino (held at bay by Dax) before he died as well. Having fulfilled their blood oath, both Kang and Koloth died glorious and honorable deaths. (DS9: "Blood Oath")

Kor, however, had a penchant for drinking and for telling stories. On one drunken occasion in a tavern on Torna IV, Kor held a group spellbound with the story of the ancient cloth and how it was going to lead him to the Sword of Kahless. One member of his audience, Toral, son of Duras, was so intrigued he sent a Lethean named Soto after Kor, aboard Deep Space 9, to steal his memories of the discovery.

Dax, Kor and Worf find the Sword of Kahless

In early 2372, Kor, with the assistance of Starfleet officers Lieutenant CommanderDax and Lieutenant Commander Worf, launched a quest to find the legendary Sword of Kahless in the Gamma Quadrant, using the data collected by the Vulcans. While unknown to them at the time, they were being trailed by Toral, who intended to steal the Sword and use it to lead the Empire.

Following the successful discovery of the Sword, the enormous symbolism of it became a matter of contention between Worf and Kor. After realizing that the Sword would only serve to further divide the Klingon Empire, rather than reunite it (as the legends foretold), they set the Sword adrift in interstellar space. (DS9: "The Sword of Kahless")

In 2375, Kor, having long been out of favor with ChancellorGowron and the High Council, and unable to secure his own command, used his remaining influence to persuade Worf to recommission him into the Klingon Defense Forces. With Worf's assistance, Kor was commissioned to serve as the third officer aboard the IKS Ch'Tang, while they made a daring cavalry raid into Dominion-held space.

Unfortunately, during this time, Kor was suffering from frequent lapses in memory and concentration, often losing track of where and when he was. At a critical moment, when both Worf and Martok were incapacitated on the bridge while engaging the Cardassian base on Trelka V, Kor suffered such a lapse. Kor believed himself to be once again engaging the Federation outpost at Caleb IV, at the side of his long dead friend, Kang. As a result of his lapse, the Ch'Tang was nearly destroyed, and the captain and first officer of their sister ship, the IKS Orantho, were killed. They were able to escape the system only to discover that they were being pursued by a fleet of Jem'Hadar fighters.

It was through the experience and bravery of Kor, and six volunteers, that the IKS Ning'tao was able to successfully engage the Jem'Hadar fleet. Realizing that the Jem'Hadar would soon overtake them, Worf had suggested using the Ning'tao to force the enemy out of warp and engage the fleet, intending to lead the attack himself. Before Worf could beam to the doomed ship, however, Kor – secretly informed by Martok's assistant, Darok – stunned him with a hypospray and took command himself. He was subsequently able to save the crews of the remaining Klingon ships, sacrificing himself to allow them the time they needed to reach the Starfleet reinforcements located in the Kalandra sector. As a salute to the fallen Dahar Master, General Martok toasted Kor, noting that he was "a noble warrior to the end." (DS9: "Once More Unto the Breach")

Kor was from a generation of Klingons not known for standing on ceremony, eating when hungry and fighting when angry. Kor had a somewhat more progressive view when it came to interactions with other species and genders. Having seen the Trill ambassador Curzon Dax as a brother, he saw no difference calling Jadzia Dax a sister, when it was time to fulfill their blood oath. (DS9: "Blood Oath") Kor displayed a calm demeanor when interviewing James T. Kirk on Organia, admitting he held a great admiration for the captain and for Starfleet of the 23rd century; Kor recognized many similarities between Humans and Klingons, seeing the killer instinct within Humanity and likening he and the captain to tigers. (TOS: "Errand of Mercy") Kor, however, felt that the Klingon social order was important, that nobility was something that Klingons in the early 24th century still held with esteem and would enforce the status quo of Klingon society by striking the name of common applicants from officer candidate lists. (DS9: "Once More Unto the Breach")

There was originally some question as to the pronunciation of Kor's name, as Kirk actor William Shatner decided the way the moniker was said should be altered. "Bill had some idea that it sounded like 'canine corps' or something like that, so he decided to change it," explained John Colicos, who played Kor in most of the character's appearances. "I said, 'But if it's going to be pronounced "Koor," then I'm going to be selling Coors beer.' So, there was a bit of palaver about that, but we wound up doing what we did because it was Bill's suggestion.'" (Starlog #138, pp. 17-18)

The script for "Errand of Mercy" details that, upon being introduced in that episode, Kor is "holding himself proud and erect and firm... obviously a man accustomed to command... a warrior."

Having worked with John Colicos before, "Errand of Mercy" Director John Newland selected him to play Kor. (Starlog #130, p. 77) Newland suggested Colicos for the part, immediately after being assigned to direct the installment. [1] Colicos was living in either Toronto or New York at the time. (Starlog #138, p. 17; Star Trek: Communicator issue 104, p. 19) He later recalled, "I got a phone call, 'Would you come out to California to do an episode of Star Trek?' I said, 'Yes, of course.' The script was sent. It arrived about two hours before I went to the airport, so I learned the lines on the plane between chicken sandwiches." (Starlog #138, p. 17) Never having heard the species name "Klingon," Colicos was extremely unsure how to portray the role. (Star Trek: Communicator issue 104, p. 19) After arriving at the Star Trek studios, he immediately went to have Kor's Klingon makeup applied for the first time. The fact that the character was meant to be an ambitious military commander led Colicos – who was given the opportunity to influence his makeup, due to it being such a last-minute job – to suggest drawing influence from Genghis Khan for Kor's appearance. (Starlog #138, p. 17)

Kor was initially to have appeared in "Day of the Dove"; the writer of that episode, Jerome Bixby, very much wanted to cast John Colicos as the installment's main Klingon character. Colicos was again offered the role and could hardly have been more excited by the prospect of appearing in "Day of the Dove". However, he was unavailable, meanwhile involved in a film being produced in Italy. (Starlog #164) According to Bixby recollecting what Colicos had said, the actor was so frustrated that he couldn't portray Kor in "Day of the Dove" (due to his film commitment) that, when he first read the episode's script, he wept, threw himself at walls, banging his head on a wall, and almost jumped off a balcony, resisting the urge to do so. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 71; Starlog #164) In fact, Colicos was twice asked to reprise the role of Kor, during the original broadcast run of Star Trek: The Original Series; Star Trek Producer Gene Roddenberry wanted to make the character a recurring one. (Starlog #138, p. 18) In a 1999 interview, Colicos admitted, "I always wonder how it all would have materialised had I been more available during the original series." (Star Trek Monthly issue 55, p. 38)

When John Colicos was needed to play Kor in "Blood Oath", DS9's casting personnel managed to quickly find the actor. (Star Trek: Deep Space Nine Companion, p. 131) Being invited to return as Kor surprised Colicos, though. "When I first read parts of the script I said, 'No, no, no, you're making a travesty of what has become a cult figure, this super marshal warrior.' I had a long talk with Michael Piller and he said I only had the first part of the script and that they were going to do this and that. He said that I was going to become a heroic figure in the end." (Star Trek: Communicator issue 104, p. 19)

One issue which John Colicos had with the script for "Blood Oath", while the DS9 producers were uncertain whether to kill off the entire trio of returning Klingons or allow one to survive, was that he wanted Kor to be kept alive. "I said, 'If one of us is left alive, then I, like Ishmael, have to be left to tell the story.' I said I didn't want to be killed off, otherwise I'd have preferred just to be remembered as the initial Commander Kor that people saw in the original series [....] I really would not have done it. The way the character evolved, I thought that unless I got some opportunity to leave in the public's mind the idea that Kor didn't just turn into a fat, old Falstaffian drunk, but that he had some heroic, redemptive qualities left in him, there was no point in my doing the show. I didn't want to destroy a whole image just for the sake of one appearance." Following much consideration and writing, the DS9 producers decided that Kor was the one who would live. "I don't know whether or not my being the first Klingon on Star Trek," Colicos mused, "influenced them in any way." (Star Trek Monthly issue 55, p. 38)

Once the "Blood Oath" script had been heavily rewritten, John Colicos was very pleased with the way it wound up depicting Kor. (Star Trek: Communicator issue 104, p. 19) He remarked, "It was fascinating, all of these years later, to come back to Star Trek, and to come back as an almost entirely different character. He'd grown into this almost Falstaffian blimp of a character." (Star Trek Monthly issue 55, p. 38) Colicos was curious how even his look had changed so drastically in the intervening years. The revised makeup involved in playing the part in "Blood Oath" regularly required Colicos to get up at 4 a.m. (Star Trek: Communicator issue 104, p. 19)

The official promotional material featuring Kor in his introductory appearance was restricted. "There is only one photograph, a head shot of me as Kor that was taken as a publicity still, so there must be many pirated pictures around," Colicos once predicted, in the late 1980s. "I keep getting color photos sent from all different parts of the world, with Bill [Shatner] and myself in a scene. People keep sending them for autographs, so it has become a very identifiable face." (Starlog #138, p. 18) In a poll to determine favorite Klingons voted by readers of Starlog (a poll which ran between issues 143 and 149 of the magazine, from June 1989 to December of that year), Kor came second to Worf. (Starlog #149) Indeed, many Star Trek fans came to regard John Colicos as the "King of Klingons," with the actor himself noting, "There seems to be a cult following on Commander Kor." Colicos also remembered that, at a 25th Anniversary Star Trek convention at Mason Phillips Square in 1991, he was given a warm welcome by the attendees, of whom there were 14,000. "I was the mystery guest. When they announced my name and I came out I thought I was the President of the United States," Colicos reminisced. "It was unbelievable." (Star Trek: Communicator issue 104, pp. 19 & 20)